This invention relates to improved boucle yarns and fabrics and processes for their preparation. The boucle yarns are prepared by combination of 2 or more components having widely different shrinkage characteristics.
Special yarns producing unusual visual and tactile effects are much in demand for the manufacture of fabrics having aesthetic properties differing from those of fabrics prepared from ordinary yarns. Such special yarns include slub or knop yarns, textured yarns and boucle yarns. Boucle yarns are characterized by a marked, stable loopiness on the surface of an otherwise plain yarn. The loops can vary in length and frequency and are ordinarily prepared from three or more different fiber components. The different fiber components may have different characteristics thus permitting the preparation of fabrics exhibiting the effect of differential dyeing, the effect of differences of denier, etc.
Known boucle yarns are ordinarily prepared by combination of at least 3 fiber components. One component is overfed to form loops, a second component serves as a core onto which the loop component is twisted and a third component stabilizes the structure by tight overwrapping. This process for making these boucle yarns is relatively slow making these yarns relatively expensive. A lower cost boucle yarn which could be prepared by a faster and simpler process would be highly desirable.
A typical process for the preparation of a boucle yarn is disclosed in U.S. Pat. No. 3,438,186 wherein a first yarn component fed at a rate almost double that of a core yarn component is wound around the core yarn component and a third component is wound in the opposite direction around the other two yarn components.
It is known to prepare composite yarns by a core-spinning process in which a staple fiber roving is combined at the front roll of the spinning frame with a yarn that may comprise continuous filaments or staple. The two components are then twisted together. This process is used, for example, to wrap a staple roving around an elastomeric yarn to form a covered yarn. Such a product is taught by U.S. Pat. No. 1,373,880 and U.S. Pat. Nos. 2,024,155 and 2,024,156. Yarns with non-elastic core components are illustrated by U.S. Pat. No. 2,526,523, which teaches feeding of a continuous filament yarn to the front rolls of a spinning frame and wrapping it with two staple fiber rovings during twisting. Use of a high shrinkage core component to provide a bulky yarn is shown by U.S. Pat. No. 2,504,523 and U.S. Pat. No. 2,218,633.
This invention provides an improved boucle yarn precursor yarn, an improved boucle yarn, boucle fabrics prepared from the boucle yarn and an improved process for preparing the precursor yarn, boucle yarn and boucle fabrics. The improved yarns need only consist of two components and can be economically prepared on commercially available equipment by a simple process.
This invention provides an improved precursor yarn having a twist multiplier of 1.5 to 4.0 suitable for the preparation of a boucle yarn comprising a core spun yarn of partially intermingled high shrinkage fibers and low shrinkage fibers twisted together, the high shrinkage fibers being predominantly on the surface of the yarn, the difference in shrinkage of the two components being at least 20% in boiling water. Preferably the high shrinkage fibers are bicomponent acrylic fibers. Most preferably the bicomponent acrylic fibers have as one component 85% by weight acrylonitrile homopolymer admixed with 15% of a 96/4 weight ratio acrylonitrile/sodium styrenesulfonate copolymer in eccentric side-by-side relationship with the 96/4 copolymer alone as the other component.
This invention also provides a boucle yarn prepared from the above precursor yarn comprised of stable loops of a spun or filament yarn or monofil component twisted tightly together with a straight spun yarn core, the boucle yarn having a twist multiplier of 1.5 to 4.0 and a loop stability of 0.2 to 1.0 inches, preferably 0.2 to 0.5 inches. Preferably the straight spun yarn is comprised of bicomponent acrylic fibers. Most preferably the bicomponent acrylic fibers have as one component 85% by weight acrylonitrile homopolymer admixed with 15% of a 96/4 weight ratio acrylonitrile/sodium styrenesulfonate copolymer in eccentric side-by-side relationship with the 96/4 copolymer alone as the other component.
This invention also provides improved boucle knit and woven fabrics.
This invention also provides a process for the preparation of a precursor yarn suitable for the preparation of a boucle yarn wherein a component consisting of a staple fiber roving of high shrinkage fibers is fed into a spinning frame and drafted in the usual manner, a component consisting of a low shrinkage spun or filament yarn or monofil is fed into the back of the front roller of the spinning frame, combined with the drafted roving and the two components are twisted together to provide a twist multiplier of 1.5 to 4.0, the shrinkage differential of the two components in boiling water being at least 20%. Preferably the roving is comprised of high shrinkage acrylic fibers. Preferably the high shrinkage acrylic fiber roving is prepared by stretch breaking followed by processing to a roving on the worsted system. Most preferably the high shrinkage acrylic fibers are bicomponent fibers.
This invention also provides a process for preparing boucle yarns or fabrics whereby precursor yarns or fabrics are heated sufficiently to achieve a differential shrinkage of at least 20% between the component fibers of the precursor yarn.
The precursor yarns of this invention may contain any high shrinkage staple fiber component combined with a low shrinkage filament or staple yarn or monofil component so long as the difference in shrinkage between the two components is at least 20%. Preferably, the high shrinkage fibers are acrylic fibers, most preferably bicomponent acrylic fibers. The precursor yarn is prepared from a roving of high shrinkage fibers, preferably prepared by stretch breaking on commercial stretch breaking equipment such as a Turbostapler.RTM. or Seydel.RTM. machine to form a sliver which is preferably drafted on the worsted system to form the roving. The roving is drafted in a spinning frame in the usual manner except that low shrinkage filament or staple yarn or monofil is combined with the drafted roving at the back of the front roller of the spinning frame followed by twisting to provide a twist multiplier of 1.5 to 4.0. The shrinkage difference between the high shrinkage and low shrinkage fiber components must be at least 20% and preferably is about 30%.
The boucle yarn of this invention is prepared by heating relaxed precursor yarn in yarn or fabric form at a sufficiently high temperature to provide the required differential shrinkage of at least 20%. Preferably, the shrinkage is accomplished in boiling water and may conveniently occur during a dyeing step. A differential shrinkage of at least 20% provides loops in the low shrinkage component which are held tightly in place by high shrinkage fibers.
Boucle fabrics may be prepared by processing precursor yarns into fabrics followed by a suitable relaxed heat treatment to provide a differential shrinkage of at least 20%. Alternatively, a boucle yarn may be prepared by relaxed heat treatment of a precursor yarn and then processing the resulting boucle yarn into a fabric. Comparable knit fabrics may be prepared by either route. Woven fabrics are best prepared from precursor yarns followed by relaxed heat treatment to form the boucle fabric.
The high shrinkage fibers can be of any type so long as their shrinkage is suffiently high to provide a differential shrinkage of at least 20% when combined with a low shrinkage fiber. Acrylic fibers are most preferred and preferably are bicomponent acrylic fibers consisting of two components in eccentric side-by-side relationship. High shrinkage polyester fibers may also be used, e.g., fibers of a copolymer of 95% by weight poly(ethylene terephthalate) and 5% by weight poly(ethylene glutarate) or partially oriented polyester yarns obtained by spinning at 3500 to 4000 yards/minute. When stretch breaking is used, in some instances, shrinkage can be enhanced by steaming the tow before stretch breaking. Preparation of the high shrinkage roving can be conveniently carried out on the worsted system from a sliver prepared by stretch breaking but may also be prepared on other systems starting with cut staple fibers.
The low shrinkage filament or staple yarn or monofil may consist of any low shrinkage fibers which in combination with high shrinkage fibers will provide a differential shrinkage of at least 20%. Yarns may be crimped or bulked but the most striking visual effects are obtained when the low shrinkage yarns are flat, i.e., uncrimped, not bulked.
A high shrinkage roving and low shrinkage yarn may be combined on any suitable spinning equipment so long as the low shrinkage yarn is added after the roving is drafted. This is conveniently accomplished by combining the low shrinkage yarn with the drafted high shrinkage roving at the back of the front roller of a spinning frame. Twisting together a high shrinkage yarn and a low shrinkage yarn does not provide the yarn of the present invention.
Twisting in the spinning machine should be sufficient to provide a twist multiplier in the precursor yarn of 1.5 to 4.0. At the most common deniers this amounts to about 8 turn/inch.
The precursor yarn is a core spun yarn of partialy intermingled high shrinkage and low shrinkage fibers in which the high shrinkage fibers are predominately on the surface.
Knit or woven fabrics can be prepared by conventional methods either from precursor yarns or boucle yarns. Shrinkage is accomplished by appropriate heat treatment and is most conveniently carried out in boiling water during a dyeing operation.
The high shrinkage and low shrinkage fibers may advantageously have different dyeing characteristics whereby variable coloring effects can be obtained in the resulting yarns or fabrics.
The boucle yarns of the present invention have highly stable loops as indicated by loop stability of 0.2 to 1.0, preferably 0.2 to 0.5 inches. The length, frequency and general aesthetic effect of the loops can be varied by modification of differential shrinkage, fiber brightness, relative size of the fibers, the type of low shrinkage yarn used, dye receptivity differences etc. between the components. Other variations will occur to one skilled in the textile arts.